Aircraft power plant control apparatus



2 shams-Smeb 1 Dec. 29, 1953 B.' A. WELLS AIRCRAFT POWER PLANT CONTROL APPARATUS Filed Nov. zo, 1949 AIRCRAFT POWER PLANT CONTROL APPARATUS Filed Nov. 50, 1249 2 Sheets-Sheet 2 Figi..

PRESSURE APPROX. ATMosPHERnc PRESSURE OPEN THROTTLE POSITION um, OF THROTTLE CLOSING R LOWE hvetor. Bruce A. Wells,

by @d Vif/r H15 Att-)ovh ey.

Patented Dec. 29, 1953 AIRCRAFT POWER PLANT CONTROL APPARATUS Bruce A. Wells, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application November 30, 1949, Serial No. 130,097

6 Claims.

This invention relates to control systems for internal combustion engines having exhaust driven turbosuperchargers, and more particularly to control systems for power plants formed by the combination with a reciprocating engine of a turbosupercharger having a variable exhaust nozzle to provide supplementary jet thrust.

The principal object of my invention is the provision of an improved control system for such a power plant.

Another object of my invention is to provide a control system for a supercharged internal combustion engine having only a turbosupercharger to provide air for supporting combustion in the engine; that is, for an engine having no gear driven supercharger to supplement the turbosupercharger.

Another object of the invention is to provide a control system for en internal combustion engine and a turbosupercharger which is operable by a single control lever.

A further object of the invention is the provision of improved means for limiting the output pressure of a turbosupercharger.

A still further object of my invention is to provide improved stabilizing means for a power plant control system.

En carrying out my invention in one form, I provide an aircraft power plant comprising a turbosupercharger connected to a reciprocating internal combustion engine in such a manner that all of the exhaust gases from the reciprocating engine pass through the turbine of the turbosupercharger. From the turbine, the exhaust 'gases pass through a variable discharge propulsion nozzle which controls the flow of these exhaust gases, the discharge ofthe gases from the nozzle providing a jet thrust to supplement the action of the reciprocating engine in turning a propeller. The compressor of the turbosupercharger is connected to the intake manifold of the reciprocating engine through a throttle and fuel metering device. The throttle and fuel metering device is operated by a throttle regulator which is controlled by a control lever. The same control lever also provides for the insertion of signals into a stabilized electronic boost control circuit which automatically governs the position of the variable discharge nozzle to maintain the air pressure at the throttle inlet at a value corresponding to the position of the control lever. Thus, a single lever provides complete control of the operation of the power plant.

For a clearer and more complete understanding of my invention, reference should be had to the accompanying drawing in which Fig. l is a schematic representation of a power plant and a single lever control system for the regulation thereof embodying the present invention in a preferred form; Fig. 2 includes a group of curves to aid in the understanding of the operation of my single lever control system; While Fig. 3 shows a typical fuel metering device and an hydraulically operated throttle regulator which may be employed in conjunction with my control apparatus.

Referring to Fig. l of the drawing, there is shown schematically a power plant 9 which may be the power plant of an aircraft. The power plant comprises a reciprocating internal combustion engine I0 provided with an exhaust gas driven turbosupercharger I2 and a variable exit nozzle 23 for the exhaust gases.

Air for supporting combustion in the internal combustion engine I0 passes into an intake duct II, then into the compressor I2a of the supercharger I2 where it is compressed, through a duct I3, an induction air cooler I4 where the temperature of the compressed air leaving the supercharger is reduced, through a duct I5 past a relief valve I6, through a throttle and fuel metering device I'I in which a throttle valve Ila is located, through a duct I8 into intake manifold I9 and thence into the engine I0.

The exhaust gases from engine IIJ pass through an exhaust manifold 20, through the turbine portion I2b of turbosupercharger I2, through an outlet duct 22 and then through a variable discharge nozzle or valve 23 into the atmosphere. The exhaust gases from conduit 22 and nozzle 23 are directed in a rearward direction relative to the flight path of the aircraft so that the reaction force resulting from discharging these gases at high velocity produces a forward thrust onv the aircraft.

The present invention is adaptable primarily to internal combustion engines of the direct injection type because of the absence of a gear driven supercharger in the air intake system between the throttle and the intake manifold. If such a gear driven supercharger is present, a conventional aircraft type carburetor can be used because of the mixing action of air and fuel provided by the gear driven sunercharger, but in the absence of the gear driven supercharger, direct iniection is ordinarily required to assure proper proportioning of the fuel among the cylinders of the internal combustion engine. The throttle and fuel metering device I'l provides means responsive to the flow of air through the throttle valve I'Ia for varying the amount of fuel injected into the cylinders. the device operating responsively to the weight of air ow through the throttle valve in a well known manner to properly proportion the mixture of fuel and air. A typical device suit able for this purpose is described hereinafter and illustrated in Fig. 3 of the drawing. The throttle and fuel metering device il is operated by a throttle regulator 2s which may also be of any well known type. Such throttle regulators are commonly operated by hydraulic means, although other types are known. A typical hydraulically operated throttle regulator is described hereinm after and illustrated in Fig. 3. The operation of relief valve i6 and its effecten theopressure in the air supp-ly duct between the turbosupercharger and the engine is also explained subsequently.

The variable discharge nozzle 23 includes adH justing eyelids which are driven by ana'lternating current motor 25 through a gear train indicated schematically at 25. The motor 25 may be of the two phase reversible induction type which operates in response to currentilowing 'through one of two eld windings, the current of one winding being displaced by 9o degrees in phase relation with the current .in the other phase by a phase shifting network 27. Such a motor is well known. The network 2 is energized by a cable at 2S connected to the airplanes source of power which may, for example, be 400 cycle alternating current. push-pull amplier 29, the circuit operation of which is hereinafter described in greater detail. In the present arrangement, all of the exhaust gases from engine i@ flow through turbine b and are discharged through variable discharge nozzle 23 to the atmosphere. The speed of turbine I2b and, hence, the output of the combined reciprocating and jet power plant, may be varied by varying the position of the eyelids of nozzle 23 to increase or decrease the ratio of pressure in eX- haust manifold 25 to the pressure in duct 22. It will be readily understood by those skilled in the art that varying the opening of nozzle 23 varies the output air pressure of the turbosupercharger I2, thereby varying the manifold pressure of enl gine l and also varying indirectly the amount of fuel supp-lied to engine I0. This varies the output of engine l, while the thrust produced by nozzle 23 is also varied because of the resulting change in flow of exhaust gases.

Variable discharge nozzle 23 is constructed so that its eyelids cannot close completely under any circumstances so that it is impossible for the boost control system to completely stop the engine. Nozzle 23 may be arranged, for example, so that it will close only to approximately of its fully open cross sectional area.

Changes in the position of the eyelids of nozzle 23 may be effected lby unbalancing a simple bridge circuit, indicated generally at 30, which forms a part of the boost control system. A transformer 3 l, energized at terminal 32 from the airplanes 400 cycle power system, supplies voltage .to the bridge which comprises a potentiometer resistor 33 and a potentiometer resistor 34 connected in parallel. The potentiometers are pro vided lwith sliding wipers 35 and 35 respectively.

`the same potential, and under these conditions Motor is energized by a voltage from a o The upper wiper .rection it is moved with respect to the grounded wiper. When such movement occurs, the bridge is unbalanced.

ln the embodiment of the invention shown in the drawing, I haveshown, by way of example, an absolute pressure responsive device which unbalances the .bridge 3Q in response to changes in pressure at the inlet of the throttle and fuel metering rdevice by moving wiper 36. This pressure responsive device comprises an evacuated bellows 38 secured at its right end to a fixed support 39 and another bellows 4t connected at its left end by a pipe 4l to duct i5. The adjacent ends of the bellowsare rigidly vjoined and are connected to wiper 36.

The pilot of theaircraftmay unbalance bridge Si) by adjusting the position of control lever 32, which moves the boost control selector so that it does not correspond with the inlet pressure to the throttle and fuel metering device. This causes a so-called error signal to be established between wiper 35 and ground, which signal is utilized, as will be seen, to reposition the eyelids of discharge nozzle 23. The error signal voltage is either in phase with the 400 cycle line voltage vor 180 degrees out-of-phase with respect to the 400 cycle line voltage, depending upon whether the actual inlet pressure to the throttle and fuel metering device is above or .below that selected by the pilot.

An error signal voltage established at bridge 39 travels through a voltage limiter 43, an adder network 44, a bias circuit 45, and a preamplifier and driver to push-pull amplifier 29, from which it emerges as an amplifier signal and is applied to the motor 25, thus causing nozzle 23 to be repositioned and the inlet pressure to the throttle and fuel metering device tobe readjusted by the turbosupercharger to the desired value. When the pressure in duct I5 at the inlet to the throttle and fuel metering device is lower than the pressure selected by the pilot, motor 25 operates to open nozzle 23. When the pressure in duct I5 is higher than the selected pressure, the opposite occurs, that is, motor 25 operates to close nozzle 23.

Under certain conditions of operation, particularly at high altitudes, the speed of turbine 2l may increase until it eventually becomes necessary tc prevent the turbine from exceeding its maximum allowable safe speed. To accomplish this, the boost control system is provided with an overspeed circuit comprising a generator #l directly connected to the turbine shaft so as to rotate at a speed directly proportional to that of the turbine. Generator 4'! may be of the permanent magnet type to provide an alternating output voltage whose frequency varies with the speed of rotation. Its output is passed through a tuned circuit 48 `to increase the yslope of the voltage speed curve in the region lof the overspeed point, thereby making the overspeed control system more sensitive when `the turbine wheel approaches'its maximum speed. Current from the tuned circuit 48 is converted to unidirectional current by a rectifier I9 and the resulting unidirectional voltage is utilized as a Variable bias voltage to control the operation of voltage limiter 43.

The voltage limiter 43 comprises essentially a peak clipping circuit for controlling the amplitude of the pressure error signal directed through it to the nozzle operating motor 25. The degree of clipping varies in accordance with the degree of 'bias voltage applied to limiter 43 from the output of rectier 49. Normally, a source of reference voltage 50 is provided to bias limiter 43, the voltage of reference U being of such magnitude that signals passing through limiter 43 normally remain substantially unchanged. However, when the turbine approaches its maximum speed and the overspeed circuit greatly supplements the bias on limiter 43 from reference source 5S, the pressure error signal is reduced substantially to zero. thus enabling the subsequent bias circuit i5 to take over and close the nozzle 23 suiiiciently to prevent the turbine speed from exceeding a safe value.

In order to insure prompt response and iiexibility of control in preventingr turbine overspeed, a xed alternating current signal Voltage tending to close variable discharge valve 23 is impressed on preamplifier 46 at all times by bias circuit 45. This fixed signal may be counterbalanced at bridge 30, preferably 'by the calibration of boost selector 35, so that the resulting signal to the valve motor 25 is algebraically zero when no change in pressure is called for. It will be evident that if the pressure error signal is reduced below the value of counter-balancing voltage at bridge 30, either by the action of the overspeed circuit, or because of circuit failure, valve 23 will automatically travel to the closed position, that is, to the maximum closed position permitted by the construction of the valve. It will also be apparent that the overspeed circuit automatically over-rules further demand for valve opening once the maximum safe turbine speed has been attained.

Due to delays in the responses which produce the actual pressure change at the inlet of the throttle and fuel metering device i '1, the controls of the system thus far described would tend to hunt and produce an undesirable fluctuating pressure, unless means were provided to overcome this unstability. I, accordingly, provide in my invention novel means for combating unstability by providing transient anticipatory signals to warn the nozzle eyelid operating motor of its approach to the position which will satisfy the demand for a change in pressure. These anticipatory signals, after being inserted in the control system, are slowly washed out electronically, after a change in nozzle position has been effected, so that no permanent droop is created in the regulation curve of the turbine.

Referring to Fig. 1 of the drawing, I provide means for obtaining a signal responsive to changes in the position of nozzle 23 by connecting the gear train 2B to a wiper 5I which moves along a potentiometer resistor 52. Resistor 52 is connected at one end 53 to a suitable source of unidirectional voltage and at the other end 5d to ground potential. rThus, the potential of wiper 5| is a value intermediate the potential at point 53 and ground potential. The nozzle position signal, derived from wiper 5I by the movement thereof, is fed to a time constant circuit 55, the output of which is fed to a chopper circuit 55.

In order to obtain an additional signal responsive to changes in the speed of turbine 2i, the

Voltage output of generator 41, in addition to being connected to tuned circuit 48, is fed through a rectifier 51 to a second time constant circuit 58. The output of time constant circuit 58 is, in turn, fed to chopper circuit 56.

The chopper circuit 56 converts the combined unidirectional transitory voltages of time constant circuits 55 and 58 to an alternating voltage which is combined with the pressure er-ror signal in adder network 44 after being passed through an amplifier 59. The chopper circuit output voltage is of the same frequency as the line, it being connected by a cable 60 to the airplanes 400 cycle system, and is either in phase with the error signal voltage or degrees out-of-phase with the error signal voltage, depending upon the polarities of the voltages from the time constant circuits, and from a, lead-lag network 62 which is discussed in detail subsequently.

Two time constant circuits are used so that the time constant for the nozzle position change signal can be of a different value than the time constant of the speed change signal from generator 41. Preferably, the time constant of the position stabilizing circuit is made considerably longer than that of the speed stabilizing circuit. When only a small pressure change occurs, the position stabilizing circuit provides all the stabilizing action that is required, but when a large change occurs, the use of the position stabilizing circuit alone might produce hunting. This is because the temporary position signal will be almost completely decayed before the desired operating position of the nozzle is reached.

In order to counteract this tendency, the speed stabilizing circuit is provided. This circuit does not come into effective operation until a comparatively long time after the original error signal, calling for a pressure increase, for example, has been introduced, because of the time delay inherent in accelerating the turbine. When the turbine acceleration finally does cause generator 47 to produce a suicient signal to overcome the short time constant of circuit 58, the nozzle eyelids are caused to move in the closed direction momentarily until the position stabilizing circuit takes over again, after which the eyelids ouickly come to rest. This movement of the eyelids occurs just before the original error signal voltage has decayed to zero so that equilibrium is once again established.

To provide for further sti` bilization of the control system, an additional follow-up circuit is used for the stabilization of the motor servo loop portion of the boost control system, which includes push-pull amplier 29 and rrotor 25. This additional stabilizing circuit includes a phase sensitive rectifier or discriminator circuit 6l and a lead-lag network 62. The alterneting voltage output of amplifier 29 is fed into the phase sensitive rectifier 5|, which produces a unidirectional voltage responsive in sense and magnitude to the alternating voltage which is supplied to motor 25. The unidirectional voltage output of rectifier 6I is fed into t-he lead-lag network 62, which produces a transient decaying voltage whose initial value is responsive to the magnitude of the voltage applied to motor 25. This network is referred to as a lead-lag network because it includes a iilter circuit which inherently introduces a lag, together with a lead producing circuit having components which insure that the ultimate output of the network is nstantcneously responsive to changes in the output of amplifier 29.

The unidirectional transitory output voltage of aces-,eea

network v62 is fed linto chopper circuit 56 where itis converted into a corresponding alternating voltage, which, after being amplified, is combined degeneratively with the error signal in adder network 4d. The effect of the yanticipatory signal produced by network El, `62 is to counteract the error signal voltage to reduce the voltage applied to the motor 25 to essentially zero when the error signal voltage is very small. This means that small momentary changes in the error signal do not cause motor 25 to operate, thus aiding materirlly in reducing hunting. When a large error voltage is present, the motor is permitted to run at full speed because the feedback voltage is then overpowered.A Also. the motor is ultimately permitted to run at full speed very soon after an error voltage of any substantial magnitude is applied because the feedback voltage is quickly washed out in the lead-lag network.

ln the selection of the throttle regulator 24 for my novel engine control system, I choose a regulator having a pressure schedule curve similar to that of the boost control system so that it is possible for a pilot to control power plant operation from a single control lever. This is illustra` ted in Fig. 2 of the drawing in which curve A represents the schedule curve of the throttle regulator, while curve B represents the schedule curve of the boost control system. Curve A indicates the intake manifold pressure, corresponding to the position of the pilots lever, that the throttle regulator attempts to maintain by varying the posiion of the throttle valve. If there is not surjcient pressure to satisfy the regulator, the throttle valve remains fully open. Curve B shows the throttle entrance pressure which the boost control system maintains at the inlet to the throttle and fuel metering .device for various positions of the pilots lever. It will be noted that curve A is slightly above curve B over the entire range, except for the lower portion. Here, the inlet pressure of the throttle and fuel metering device has a lower limit corresponding approximately to sea level atmospheric pressure and the schedule curve of the throttle regulator drops below curve B. Over the remainder of the operating range, however, curve A is above curve B, which means that the throttle remains fully open at alltimes under ordinary night conditions.

Curve C in Fig. 2 represents the actual position of the throttle valve corresponding to the various positions of the pilots control lever, while curve D represents the closing limit of the throttle valve beyond which it is mechanically impossible for the throttle to go. 'It will be readily understood by those skilled in the art that the limit represented by curve D is necessary to provide for engine starting, to prevent the throttle from being suddenly closed completely, and for other reasons of safety, and that all conventional throttls regulators include this feature.

There is shown in Fig. 3 ofthe drawing a schematic diagram of a typical throttle regulator and a typical fuel metering device suitable for use in the aircraft power plant control apparatus disclosed herein. These devices and other associated parts bear the same reference numerals in this ligure as in Fig. 1. As shown in Fig. 3, the throttle regulator 24 comprises a hydraulic cylinder lli having a piston 'll connected for the operation of throttle valve Ila through a piston rod l2 anda lever arm 13 connected to the throttle valve. Piston il is operated to the right or left to move throttle lla toward its closed and opened positions respectively, by means of a hydrauiic relay device lllhaving a slidable operating member 1.5 operated by a rod The latter is connected for operation by a pivoted member 'il which is acted upon by two forces, one due to a tension spring 78 and another due to the pressure differential created by a bellows it and an evacuated bellows B. This throttle regulator operates to `maintain a predetermined throttle valve position depending upon the position or" control lever 42, the position of this control lever determining the tension in spring l. Assuming, for example, that the pilots control lever is moved clockwise thereby increasing the tension on spring T8, .lever will be rotated clockwise which Iwill move the rod l5 and operating member 15 of relay device lil to the left. This will admit oil or other hydraulic fluid on the side of piston l! and rotate throttle valve llc counter-clockwise, thereby increasing the opening of the throttle valve. The increased opening of the throttle valve will increase pressure in duct I8 from which a pressure transmitting line 93 is connected to bellows lil. The resulting increase in pressure in bellows 'it tends to restore lever 'Il Yto its initial position and thereby attempts to restore the throttle regulator to equilibrium. Throttle valve lla would thus normally be maintained at a position correspon ng to the pressure selected by pilots control iev fil?. to provide a selected manifold pressure as indicated by the curve A of Fig. 2 if it were not for the boost control system which prevents such action during normal operating conditions or the aircraft power plant control system. There is also shown as a portion of the throttle regulator' of Fig. 3 a connection between control lever l2 and a cam 3l which provides the minimum throttle valve closing position corresponding to curve D of Fig. 2. Due to the mechanical connection between control lever i2 and earn el, there is provided a lower limit of throttle closing corresponding to the throttle lever position which is independent of the action of either the throttle regulator 24 or the boost control system.

There is also shown in Fig. 3 a fuel metering device which is suitable for use with the system disclosed herein. As shown schematically, this device comprises four pressure chambers 82, 83, Sli and 85. Chambers 32 and 83 are separated by a ileXible diaphragm 85, and chambers 8d and are separated by flexible diaphragm 8l, while chambers S3 and 231i are separated by nxed wall member 88. Elongated slidable member 89, having a xed connection with diaphragms 8d and 8l and a slidable connection with a wall 88, is positioned centrally of the device as shown in Fig. 3. Two pressures derived from the air ilow through the air inlet duct to the internal cornbustion engine are applied to chambers 32 and 83. The pressure in chamber 82 varies approximately directly with the velocity in the air of duct I5, this pressure being derived through a tube Si) which has its inlet positioned so that the air stream impinges directly on it. The pressure in chamber 83 varies non-linearly with the velocity of the inlet air stream inasmuch as this pressure is derived from a tube 9i which is connected to a Venturi tube 92 in the duct i5. Thus, there is a pressure differential between chambers 82 and 83 which is dependent upon the velocity and hence varies with the volume or weight of air flow into the manifold of engine iii. Chamber 535 of device il receives fuel under pressure from the engine fuel pump when the shoulder portion of chamber 8S Vis separated from its seat against wall 93 of the device. From chamber 85, fuel passes through a connection 84 having therein an orifice 95 to the fuel injection pump or pumps for the cylinders of engine I0. The size of orifice 95 is set by the pilots mixture control lever (not shown). 'I'he outlet from orifice 95 communicates with chamber 94, thus providing a pressure differential between chambers 84 and 85 which is dependent upon the amount or weight of fuel flow through orifice 95 to the fuel injection p-umps and into the engine cylinders. In the operation of device l1, the pressure differential between chambers 82 and 83 acting through diaphragm 86 balances the pressure differential between chambers 84 and 85 acting through diaphragm 81 and maintains a weight of fuel fiow to engine l which is responsive to the weight of combustion air entering the intake manifold.

During normal flight operation, the throttle remains fully open and the entire power plant, including engine I 0, is governed completely by the boost control system. When the pilots lever is moved close enough to the zero position that curve A drops below curve B, then the position of the throttle valve changes in Aaccordance with curve C to maintain the intake manifold pressure in accordance with curve A, with the throttle gradually closing as the pilots control lever approaches the zero point.

In order to prevent the air pressure output of the turbosupercharger from exceeding the desired maximum pressure limit during emergencies such as a failure of the electrical control system, for example, I provide relief valve I5, previously mentioned. This valve is of the spring loaded pop-off type and is provided with an evacuated bellows 64 having approximately the same effective cross sectional area as the area of the valve seat, so that regardless of altitude the relief valve operates at the same absolute pressure. The biasing spring 63 may be conveniently located within the bellows 64, if desired. When the pressure within duct I gets sufficiently high, the bias of spring 63 is overcome and member E5 leaves the valve seat and releases air to the atmosphere.

It will be understood that as the air pressure output of the turbosupercharger increases abnormally above the normal operating range, the throttle valve is immediately operated as soon as the intake manifold pressure exceeds curve A. This is effective only to a limited extent, however, in counteracting an abnormal pressure rise because of the lower limit of throttle closing, as illustrated by curve D. Furthermore, if the output of a centrifugal compressor is throttled too much, -a surge condition is encountered under which the pressure oscillates violently from one extreme to the other, and this provides another limit on the amount of throttling by valve lla.

In order to surmount these obstacles and keep the power plant operating under emergency conm ditions such as the failure of the electrical control system, I provide valve l6 which opens and releases air to the atmosphere when the pressure in duct l5 reaches a predetermined absolute value. Valve I6 is so chosen that it is easily cap-able of releasing sufhcient air to the atmosphere to prevent the building up of enough air pressure to damage the engine and at the same time to prevent the turbine from running away, Since the air which passes into the internal combustion engine ultimately reaches the turbine in the form of exhaust gases, the release of sufiicient air from the induction line causes the turbosupercharger to reach an equilibrium operating condition at which the power supplied by the turbine equals the load created by the compressor, which means that the turbine speed does not increase further and it is prevented from running away.

It may be pointed out that single lever control, as provided by this invention, is particularly advantageous for a power plant of the type illustrated in Fig. l which has no gear driven supercharger to supplement the action of the turbosupercharger. When a gear driven supercharger is used, there is some supercharging action present 'whenever' the reciprocating engine is running, regardless of the condition of the turbosupercharger. Thus, it is possible to operate the internal combustion engine at reduced power without using the turbosupercharger at all. When 'there is no gear driven supercharger, however, the turbosupercharger must be operated in order to operate the internal combustion engine. Therefore, it is important to provide a control system which provides for operation of the complete engine and turbosupercharger unit by means of a single control lever.

While I have illustrated and described a preferred embodiment of my invention, modifications thereof may be made by those skilled in the art and, therefore, it should be understood that I intend to cover, by the appended claims, any such modifications which fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a power plant having an internal combustion engine for providing the primary source of power, an exhaust gas driven turbosupercharger, and a variable nozzle for controlling the flow of exhaust gases to provide a supplementary source of power in the form of a jet thrust, a control system comprising a throttle valve in the air supply duct connecting said turbosupercharger and the intake manifold of said engine, a control lever, means for maintaining a preselected throttle entrance pressure in said air supply duct comprising means responsive to changes in turbosupercharger pressure for producing an electrical error signal proportional to the difference between said throttle entrance pressure and a preselected pressure corresponding to the position of said -control lever, means responsive to said error signal for positioning said nozzle to maintain said preselected pressure, electrical stabilizing means connected to said error signal responsive means for generating a transient anticipatory signal, network means connected to receive and add said anticipatory signal in opposition to said error signal, and throttle regulator means controlled by said control lever for positioning said throttle valve responsively to the engine manifold pressure, said throttle regulator means providing higher pressure values than said throttle entrance pressure maintaining means for a selected range of control lever positions in the normal operating range of said control system whereby said throttle valve is maintained fully open during normal operation.

2. In a power plant having an internal combustion engine provided with an exhaust driven turbosupercharger, a valve for controlling the flow of exhaust gas through the turbosupercharger, a control lever, a throttle valve in the induction air duct connecting said turbosupercharger to the intake manifold of said engine, a throttle regulator controlled by said control 11 i lever for positioning said throttle valve responsively to. the intake manifold pressure of said engine, means responsive to the owof air through said throttle valve for supplying fuel to said engine, and a boost control system responsive to the air pressure between said turbosupercharger and said throttle valve, said boost control system comprising means for deriving an electrical error sig-nal responsive to changes between said air pressure and a preselected pressure corresponding to the position of said lever, and electrical means responsive to said error signal for positioning said valve to vary the output of saidy turbosupercharger and thereby maintain said preselected throttle entrance pressure, said boostcontrolsystem providing pressure values lowerv than said. throttle regulator for a selected range of control lever positions inthe normal operating range of said control apparatus whereby said'throttle valve is maintained fully open by said throttle regulator during normal operation.

3. Ina reciprocating engine having an exhaust driven turbosupercharger adapted to utilize substantially ali the exhaust gas produced by said engine, said turbosupercharger being provided with a variable nozzle on the outlet of the turbine portionthereof for controlling theA output of said turbosupercharger, and an air supply duct connecting the compressor portion of said turbosupercharger to the intake manifold oi engine, the combina f, ofr a control lever, a throttle valvel in said su' ply duct, ay hydraulic regulator connected to controllever for positioning said throttle valve responsively to the manifold pressure andthe position, of said lever. and a boost control system responsivel tor thev pressure in saidlsupply` duct upstreaml fromV said throttle valve, said boost control system comprising` electrical meansconnected to` said lever for deriving an error signal responsivev to the, difference ben tween fsaidsupply duct pressure and a preselected pressure corresponding to the position of said lev and electrical meansv responsive, to said signal for o,c s ti0r111sv Said, turbosupercharger elise/lia:rgef valve to maintain said supply ductpressurey atl said preselected value.

4;'. In a supercharging andfcontrol system for internal, combustion' engine,V a superCha-rger drivenlb'yy anaexhaust gasturbine, a valve for con trollingthejexhaust gras, flow through said turbine, po tioningV ans for saidvalve, electrical control means compv ing means for sensing the pressure ofi air supplied by said supercharger, bridge means for deriving anA alternating4 error voltage proportional to the, difference between the sensed pressure and a selected pressure, alternatingv current generator means, connected to said turbine for restricting the error voltage when said turbine Y 'roaches' a predetermined speed, a rst stabi-V liz'i fg circuitl including-v said generator means for producing avrst stabilizing voltage in phase op.m position to, saidY alternating error; voltage, said rst stabilizing circiut. comprising rectifier means connected to saidgenerator means and atime constant circuit connected tosaid rectifierv means for providing a transient voltage having a. predetermined time constant a second stabilizing circuit responsive tothe position of said valve for producing, a second stabilizing voltage in phase opposition to said alternating error voltage, said second stabilizingA circuit comprising a potentiometer operated by said valve positioning means and a time constant circuit having a longer time constant than` the. time constantv circuit included in said first stabilizing circuit for providing a second transient voltage, network means for coin= bining said two transient voltages, means for con verting the combined voltage to an alternating voltage, means for combining said converted voltage with said error signal in opposition thereto, means for amplifying the difference between said error signal and said converted voltage, and means for operating said valve positioning means in response to said amplied voltage.

5 An apparatus for controlling the pressure of combustion air supplied to an internal combustion engine comprising an exhaust gas driven turb-osupercharger, a variable nozzle for controlling the flow of exhaust gases driving the turbosupercharger, means responsive to changes in the air pressure supplied by said turbosupercharger for producing an error signal voltage proportional to the difference, between the pressure of air discharged rom said turbosupercharger and a preselected pressure, motor means for the operation of said nozzle, amplifier means responsive to said error signal voltage for operating said motor means and said nozzle to maintainrsaid preselected pressure, means for deriving a rst transient stabilizing voltage responsive to changes in the output voltage of said ampliiier means, a stabilizing circuit including a generator driven by said turbosupercharger for providing a second transient stabilizing voltage responsive tochanges in the speed o' said turbosupercharger, a stabilizing circuit responsive to changes in the position of said nozzle for producing a third stabilizing voltage, network means for combining said three stabilizing voltages, and means for applying, said combined voltages in opposition to said error signal voltage so that only thev diii'erence between said error signal voltage and said combined voltages is available for actuating said amplifier means.

6. An apparatus` for controlling the pressure of combustion air supplied to an internalA combustion engine comprising an exhaust gas driven turbosupercharger, a variable nozzle for controlling the flow ci exhaust gas, means responsive to changes in the air pressure supplied by said turbo-supercharger for producing an error signal voltage proportional to the difference between the discharge pressurev and a preselected pressure, motor meansA for the, operation of said nozzle, amplier means responsive to said error signal for operating said motor means and said nozzle to maintain said preselected pressure, means for deriving a transient anticipatory voltage responsive to changes in the output voltage of said amplier means, a generator driven by said turbo,- supercharger, a time constant circuit connected to said generator for providing a rsttransient stabilizing voltage responsive to changes in the speed of said turbosupercharger and having` a predetermined time constant, a second. stabilizing circuit responsive to changesr in the.v position of said nozzle for producing a second` transient stabilizing voltage, said second stabilizing circuit including Aa second time constant circuithaving a different time constant than said rst time constant circuit, networkA means for combining said anticipatory voltage and said two stabilizingvoltages, andmeans for applying said combined voltages in opposition to said error signal voltage in a manner such that said amplifier means is-responsive only to the difference between said error signal and said combined voltages.

BRUCE A.

(References on followingV page) References Cited in the me of this patent UNITED STATES PATENTS Number Name Date Levy et a1 May 15, 1934 f, Hull Mar, 4, 1941 Anxionraz et a1. Aug. 22, 1944 Burnell Mar. 27, 1945 Baak Aug. 17, 1948 Alexanderson Nov. 9, 1948 10 Number Number Name Date Bedford Feb. 22, 1949 Gille Nov. 8, 1949 Kutzler Dec. 13, 1949 Crum et al. Jan. 3, 1950 FOREIGN PATENTS Country Date Great Britain Nov. 20, 1945 

